This invention relates generally to the forming of thin metal parts and particularly to a method of detecting the forming of faulty parts in a press using progressive dies.
Many thin metal parts, such as the parts for the electron guns of color television picture tubes, are made using progressive dies. Such presses include a plurality of forming stations, with each station including a forming tool and a die. The forming tools and dies are configured and dimensioned so that a different operation is performed at each forming station. A strip of material is fed through the press to sequentially pass each of the forming stations. The number of forming stations is determined by the number of forming operations needed to form the part. Typically, all the forming tools are driven by a common ram so that every forming operation is performed for each stroke of the ram. The strip is inserted into the press in alignment with the first forming station and the first operation is performed. The strip is sequentially incremented past every forming station and when the beginning of the strip passes the last forming station the forming of the first part is completed. Accordingly, after the first complete part is formed, each stroke of the ram results in the formation of one complete part.
Changes in a wide variety of uncontrollable characteristics can cause the formation of defective parts. For example, changes in the thickness of the metal strip from which the parts are formed, flaws in the metal, wear on the forming tools and dies, and foreign matter on the metal strip can cause either the formation of defective parts, or damage to and breaking of the forming tools. There, therefore, is a need for a system and method for detecting the formation of faulty parts to either stop the forming press, or to permit the collection of data for analysis to correct the problem causing the defective formation. The present invention fullfills this need.